1. Field of the Invention
The present invention relates to a line segment construction device for construing the attribute information (e.g., the category) of line segments that constitute a line figure, such as a map or a system diagram.
2. Description of the Related Art
In a conventional figure generating apparatus for generating and editing a line figure, such as a system diagram of computer aided design (CAD), it is desired that the data on the line segments of a line figure be processed with high efficiency. For high-efficient processing, the attribute information (e.g., the category) on the line segments of a line figure is entered in a computer.
In this type of figure generating apparatus, a line figure is displayed on the screen. While looking at the line figure on the screen, the operator designates a given line segment by means of a mouse, a digitizer, or the like. The operator judges the attribute information on the designated line segment by visually confirming the relationships which the line segment has with reference to the other line segments, and manually enters the result of the judgment.
In the above figure generating apparatus, the operator has to judge the attribute information on all line segments of a line figure by visually confirming the relationships of each line segment to the other, and to manually enter the result of the judgment. Accordingly, the data input operation is very troublesome, and the operator has to concentrate his or her attention on the data input operation. If the operator's power of attention decreases, it is likely that data will be entered incorrectly, adversely affecting the accuracy of the attribute information. If it is necessary to occasionally warn the operator to direct attention to the data input operation, the time needed for the data input operation is lengthened, accordingly. As a result, the efficiency of the data input operation lowers, and the cost of the resultant line figure will be high.
One of the ways for solving the problems may be to provide the apparatus with a function of automatically determining the attribute information on the line segments of a line figure. If, in this case, each of the line segments of a line figure is examined singly, it is not possible to obtain information sufficient for reliable determination of the category of the line segment. In other words, the category of each line segment has to be determined on the basis of symbols and characters located in the vicinity of the line segment, the relative position of the line segment to the other ones, and the manner in which the line segment is connected to other ones. A computer may be used for the recognition of symbols and characters, but recognition by means of a computer is not very reliable. It sometimes happens that a computer will incorrectly recognize symbols and characters. If the symbols and characters are incorrectly recognized, the category of the line segment related to them cannot be determined until the categories of the other line segments are determined. In this manner, the information input to the computer is indefinite, and decision theoretic inference may not be carried out only with the information input to the computer.
The techniques related to the present invention are disclosed in H. Bunke et al, "PROBABILISTIC RELAXATION FOR INTERPRETATION SCHEMATICS", Proceeding of Pattern Recognition and Image, pp. 438-440 and M. Gerald et al., "Discrete Relaxation Applied of Technical Documents", Proceeding of ICPR, pp. 706-708.